In financial markets, transparency of financial information is one of the most effective variables of investment strategies. Information asymmetry can seriously affect firm performance on the stock exchange and firms with a poor informational environment can lose the interest of investors. Reducing information asymmetry can have an important effect on firm performance on the stock exchange. Firms may lack a clear informational environment in the market because of the emerging conditions governing the Tehran Stock Exchange. Because larger and more active firms on the Tehran Stock Exchange provide more information, measuring the informational environment of these firms provides an overview of information asymmetry. The present study calculate...